Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 161548

Area Forecast Discussion
National Weather Service Gaylord MI
1048 AM EST Thu Nov 16 2017

Issued at 1047 AM EST Thu Nov 16 2017

Pressure gradient overhead is starting to relax as departing
surface low pushes farther into Quebec. Winds will therefore
slowly start to diminish heading into the afternoon, but still
remain somewhat gusty until this evening. Wind direction will
slowly shift from NW to N through the day, which will eventually
nudge lingering bands of lake effect showers this morning to near
and south of Grand Traverse Bay. As is par for the course here in
northern Michigan, these lake effect showers are holding on longer
than earlier expected, but they will continue to decrease in
coverage and intensity over the next few hours as Canadian high
pressure and a very dry airmass progressively nose in from the
northwest. This is slowly drying out the column from top down, and
by early afternoon the moisture depth should be too shallow to
support any continued precipitation.

Some breaks in the clouds already showing up on vis satellite, and
these should become more commonplace this afternoon, especially
over eastern Upper and northeast Lower. Temperatures will remain
nearly steady-state during the day but will drop quickly this


.NEAR TERM...(Today through Tonight)
Issued at 250 AM EST Thu Nov 16 2017

...Improving conditions today...

High impact weather potential...Not much. Still expecting some lower
end gale gusts on some of the big waters today.

Pattern synopsis/forecast...Progressive pattern of late continues,
with overhead shortwave troughing/attendant surface low racing off
to the east, all-the-while mid level ridge axis and its surface
likeness build into the northern Mississippi Valley. While synoptic
support is decreasing, lingering backside moisture and just enough
cold air advection to drum up a bit of lake response continues to
produce a rain/snow shower mixture, centered particularly across
eastern upper and northwest lower Michigan. Despite some decent snow
rates where precip has fully changed over, above freezing surface
conditions has kept any snow accumulations minimal. Rapid drying
taking place just to our west, getting set to punch into our area as
that upstream ridge does the same today and tonight.

Primary forecast concerns/challenges: Addressing ending of lingering
rain/snow showers this morning and temperature/cloud trends both
today and tonight.

Details: While deep layer synoptic scale moisture departure is a
swift one, lingering lake processes likely to keep a bit of light
rain/snow shower activity in those traditional lake belts for a few
hours this morning. Rapidly building mid level heights and arrival
of surface high pressure looks to put an end to any lingering
showers by early afternoon. Clouds likely to be a bit slower to
break up, a trend well evident per satellite observations showing an
expansive stratus field all the way back into Minnesota. Suspect
these will start to erode during the afternoon, allowing most areas
to experience a bit of sunshine by days end.

Mid level ridge centers itself directly overhead tonight as the
surface high pushes just off to the east by sunrise Friday. Warm air
advection starts to ramp up late, brining increasing high and mid
level clouds. H7-surface layer never saturates, keeping any
developing late night rain and snow to our west.


.SHORT TERM...(Friday through Saturday)
Issued at 250 AM EST Thu Nov 16 2017

...Rain transitions to snow this weekend...

High Impact Weather Potential: Somewhat gusty winds expected to
develop Saturday with rain transitioning to snow, although not
expecting too much impact through Saturday afternoon (though
slightly cooler temps aloft could yield a different story).

Pattern Forecast: By Friday morning, ridge axis firmly overhead will
shift east as low level warm air advection ramps up. Digging
longwave trough across the western third of the CONUS will become
the focus through the weekend as cyclogenesis gets underway lee of
the Rockies during the day Friday, quickly racing northeastward into
the Western Great Lakes Friday night. As a result, another round of
widespread precipitation is anticipated Friday afternoon through
Saturday, with colder air and increasingly gusty northwest winds
wrapping around the back side of the system by Saturday afternoon as
low pressure progresses into southern Ontario.

Primary Forecast Concerns/Challenges: Precipitation arrival Friday
along with occasional precip type issues, mainly in eastern upper and
over the higher terrain.

Increasing low level jet throughout the day Friday is expected to
yield healthy moisture return with PWs progged to climb to 0.75-
1.00" across all of northern Michigan. Isentropic ascent and
attendant northward moving warm front should be sufficient to
trigger scattered/light showers across sections of northern WI and
western upper MI early Friday morning (perhaps clipping far northern
reaches of the forecast area around midday) before shower coverage
expands from west to east across the remainder of northern Michigan
Friday afternoon into early Friday evening.

Widespread showers are expected for the remainder of Friday evening
into Friday night with precip coverage/intensity waning a bit toward
Saturday morning. However, another surge of moisture is expected to
slide northward across the area late Saturday morning into the
afternoon, associated with increasingly favorable upper level jet
structure and approaching mid level trough axis. As colder air
filters into the region behind the system`s cold front throughout
Saturday afternoon, deformation precip could become enhanced by a
combo of increasing lake processes and developing gusty northwest

With respect to precip type throughout the event, predominantly rain
is expected for most as precip arrives Friday, although a rain/snow
mix remains possible across sections of eastern upper and the
interior/higher terrain of northern lower. Per forecast soundings,
sub 1,500 ft. temps are expected to rise Friday night, in
conjunction with continued low level WAA ahead of low pressure
crossing overhead early Saturday, likely transitioning any lingering
mixed precip to all rain. Falling temperatures by early Saturday
afternoon will allow for a rain/snow mix in the higher elevations,
transitioning to all snow mid-late afternoon. Interesting to note
that if temps aloft cool another degree or two than currently
progged early Saturday afternoon, a transition to all snow much
earlier in the day would be a possibility...and thus higher
accumulation of wet/heavy snow. However, as it stands now, only
minor snow accumulations expected through late Saturday afternoon
with additional lake effect snow possible Saturday night-Sunday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 250 AM EST Thu Nov 16 2017

High impact weather potential: Accumulating lake effect snow
possible Saturday night into Sunday.

A cold Canadian airmass continues to pool into to northern Great
Lakes Saturday night into Sunday. Over-lake instability and gusty
northwest flow will be sufficient to produce lake effect snow
showers; however, some uncertainties around potential snow amounts
still exist. Plenty of instability (delta Ts around 20 C) and
respectable inversion heights certainly aid the cause, but the lack
of an overly persistent low level flow and omega displaced from the
DGZ may keep accumulations from getting too out of hand.

By late Sunday into early Monday, increasing heights aloft and the
arrival of surface high pressure from the southwest is expected to
gradually shut down lake processes. After a brief break in the
active weather, another quick-moving, but potent system may impact
portions of the Great Lakes with more wintry weather.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 620 AM EST Thu Nov 16 2017

MVFR producing cigs expected to continue for several more hours,
with some slow improvement expected this afternoon. Cigs scatter
out some later today, with some increasing high and mid level
clouds overnight. May see a few light showers/snow showers impact
the locations yet this morning, with dry conditions expected
otherwise. Gusty northwest winds will slowly subside today. Winds
steadily veer to east and southeast tonight.


Issued at 1047 AM EST Thu Nov 16 2017

With pressure gradient relaxing, gale force gusts have become few
and far between over northeast Lake Michigan and Whitefish Bay.
Have therefore gone ahead and replaced the Gale Warning for those
nearshore zones with a small craft advisory through 6 PM. Some
gale force gusts still expected along Lake Huron this afternoon,
so will continue the warning there. Otherwise gusty northwest
winds slowly subsiding through the rest of today as they become
northerly, leading to a brief period of rather light winds this

South to southeast winds ramp up quicky later tonight and
Friday as the next system begins to take shape to our west. Passage
of this system will likely bring a period of very gusty northwest
winds to all waters this weekend.


LH...SMALL CRAFT ADVISORY until 6 PM EST this evening for LHZ345-346.
     GALE WARNING until 6 PM EST this evening for LHZ347>349.
LM...SMALL CRAFT ADVISORY until 6 PM EST this evening for LMZ323-341-
LS...SMALL CRAFT ADVISORY until 6 PM EST this evening for LSZ321-322.


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